The present invention relates to a thermoelectrically powered wrist watch in which the energy generated in a thermoelectric element, making a thermoelectric conversion by using the difference between the human body temperature and the outside air temperature at the time when a person has put the wrist watch on his arm, is used as a power source for actuating the hands thereof.
Conventionally, there is known a thermoelectrically powered wrist watch such as that disclosed in Japanese Patent Application Laid-Open Publication No. 55-20483. That is, as illustrated in FIG. 2, a heat insulation member 30 is disposed at the side surface of a case, and the heat absorbed from the outside through a case back 150 is transferred to one end of a thermoelectric element 3 which is a thermoelectric generator, through a metallic plate 31 which is an elastic member.
On the other hand, the heat absorbed into the case is radiated from the other end of the thermoelectric element 3 to the outside through a shock absorbing member 32 consisting of a metallic elastic member, an intermediate ring 33 constituted by a metallic ring, a dial 6, an exteriorly equipped recess padding edge 34, etc.
The above-constructed thermoelectrically powered wrist watch can supply thereto a larger amount of heat energy by absorbing heat from a wearer's arm through a bottom portion of the case having a large area.
In the conventional thermoelectrically powered wrist watch, since a larger amount of heat energy is absorbed into the case, it is necessary to prevent the occurrence of the phenomenon that the temperature inside the case rises with the result that the temperatures at both ends of the thermoelectric element 3 are brought into equilibrium with each other, i.e., the temperature difference between the both ends thereof becomes zero, resulting in that the thermoelectric element 3 is brought to a state capable of generating no power.
On this account, in order to radiate the heat from a glass 7 or recess padding edge 34 to the outside of the case with a high efficiency, a heat insulation member 30 made of plastic material or the like had to be provided at the side surface of the case so as to insulate the heat absorbed from the bottom surface of the case.
Therefore, it is necessary that the case itself be constructed of two parts, i.e., heat insulation member 30 and recess padding edge 34. That is, the case itself becomes unable to be finished to a solid or one-piece metallic case. In consequence, the outer appearance of the case looks inferior and further the manufacturing cost thereof also increases.
Further, with the radiating means which uses the glass 7 having a low thermal conductivity, the recess padding edge 34 having a small surface area and the like, it is impossible to perform sufficient radiation of the heat inside the case, with the result that the temperature equilibrium is inconveniently established inside the case and as a result the thermoelectric conversion efficiency becomes inconveniently low. In addition, covering the entire circumferential side surface of the case by the heat insulation member 30 having a high heat insulating effect, also, causes a decrease in the thermoelectric conversion efficiency.